1. Subatomic Particles protons, neutrons and electrons

2. Cathode Ray Tube Tube used to study the relationship between mass and electric charge Cathode = negative; anode = positive Crookes and radiation from cathode to anode Led to the development of the t.v. and computer

4. Dalton’s atomic theory proven wrong… Atoms are divisible into smaller subatomic particles Thomson discovers the first subatomic particle – electron!

6. The Charge of an Electron Discovered by Robert Millikan Mass = 9.11 x 10 -28 grams Led to several questions: Where does the rest of the mass of the atom come from? How is all matter neutral if electrons are part of all matter and electrons have a negative charge?

7. Plum Pudding? Thomson – electrons distributed throughout a uniform positive charge

8. Gold Foil Experiment and the nucleus Ernest Rutherford Gold Foil Experiment disproves plum pudding New model – atom is mostly empty space through which electrons travel Tiny, dense nucleus containing the mass of the atom An atom the size of two football fields would have a nucleus the size of a nickel A mass of nuclei the size of a period would have a mass of 120 tons Positive charge of nucleus balances negative charge of electrons

9. Protons and Neutrons Chadwick discovers the neutron – mass equal to proton but does not carry a charge Atoms are spherically shaped with a tiny, dense nucleus of + charge surrounded by – charged electrons traveling through empty space surrounding the nucleus

12. Properties of Subatomic Particles ParticleSymbolChargeMassLocation Electrone -1 -1/1840 amu (0) Space surrounding the nucleus Proton p +1 +1 amuIn the nucleus Neutronn 0 01 amuIn the nucleus

13. Isotopes Atom with the same number of protons but different numbers of neutrons Change the # of protons = change the element Change the # of electrons = happens all the time Change the # of neutrons = change in mass number = isotope of the atom